A wide variety of fish products which provide a ready source of processed fish are now available. Surimi is one such product. Surimi is a paste of minced, washed fish muscle. The washing removes water soluble components as well as removing other contaminants. High quality surimi consists of a paste of such muscle. This is dissolved in a dilute solution of sodium chloride which gels on heating. The surimi can be shaped when in a paste form or shaped and extruded after cooking. The surimi paste is usually provided in frozen form. Substances known as cryoprotectants are added to the surimi mix prior to freezing to increase its storage stability. However, a number of species of fish contain heat stable proteases which break down muscle texture during processing, and thus inhibit the gel forming ability of surimi. Since gel formation is a critical processing requirement, species with heat stable proteases are unsuitable raw materials for the production of acceptable quality fish products such as surimi.
A large number of fish species exhibit protease activity which make them unacceptable for preparing processed fish products. Fish species that contain one such enzyme, alkaline protease, include Hoki and Atlantic Croaker. To date, these fish species, which are in plentiful supply in some parts of the world, have been unsuitable for use in the preparation of surimi.
With the growing demand for imitation seafood products made from surimi, new processing technology is essential so that new sources of fish material can be utilized. Based upon the large numbers of species exhibiting proteolytic activity, suitable protease inhibitors would be an indispensable tool in fish processing technology.